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Particle Accelerators and huge tanks
Gigantic, fascinating experiments are being performed every day in many different places on our planet, by thousands of scientists. We discuss some of the most impressive aspects of cutting edge particle accelerators and other large man-made machines..
Giant microscopes
There is a golden rule in small scale physics that says that the smaller the object is that you want to study, the bigger the machine is that you need to study it. We can easily see a kitchen table, for instance, with as small an apparatus as our naked eye. When we want to study cells of our body though, we need an extension, called a microscope. To see even smaller objects, like the atoms the cell is made off, we need even bigger machines, for instance Scanning Tunneling Microscopes, that can feel the presence of an extra atom on a surface through an electric current it induces through a needle that hovers over the surface.We have been talking about even much smaller objects though. A nucleus of an atom is ten thousand times smaller than the atom itself. (One could think of the electron clouds as occupying the space between atomic nuclei in the air, the kitchen table, and everywhere where there is matter.) Roughly, the apparatus that we need to study these nuclei and the particles within them is about ten thousand times bigger than the machine we needed to see an atom. The microscope that lays bare the secrets of the atomic nuclei, the particle accelerator, has a length in the order of kilometers. Thus, we can think of particle accelerators as giant microscopes. Note that the largest structure we can build on earth would be about ten thousand times bigger. Out there, in the universe, we have of course a lot more room.
Why is it that we need bigger machines to observe smaller structures
? Well, almost always when we say we observe something, it is through
indirect means. We don't see the kitchen table itself, but we see the
light that is reflected on its surface. (The kitchen table itself does
not fly towards our eyes.) The sun shines photons on the surface of the
table, which reflects or absorbs it in its own characteristic fashion,
and from the little information that comes our way we can deduce that
we are dealing with a kitchen table. 
Thus, we can send a beam at an object and observe what kind of radiation or particles come out. We can send small particles at an atom and observe that the atom only significantly scatters the small particles when these particles hit the nucleus -- otherwise they fly past almost unaffected. From that we can deduce that an atom is made of a huge cloud of electrons and a tiny nucleus.
One property we need when we send a beam at an object to observe its
structure, is that the characteristic probing wavelength of the beam is
smaller than the object. Indeed, suppose we send a long wavelength electromagnetic
beam at a tiny target. Than it is fairly obvious that the beam will miss
the object entirely. (In fact, radiowaves for instance have no effect
on the atoms in our body.) For a tiny object, we need an electromagnetic
beam with an even tinier wavelength to be able to observe the substructure
of the object. Otherwise, the outgoing scattered waves will carry no information
about the substructure of the object under study. 
Next we note that the shorter the wavelength of the electromagnetic radiation, the higher the frequency (since the product of the frequency and the wavelength is equal to the speed, which is the constant speed of light), and the higher the frequency, the more energy is stored in the radiation. (Imagine having to produce a high frequency wave by moving an electron up and down very fast -- it will cost you a lot of energy.) Thus, the higher the energy of the incoming beam of radiation, the smaller the structures we can probe.
The mechanism in accelerators is slightly different than the one just described, but the basic law that we derived remains valid. The total energy in the incoming beams will be an excellent measure for the distance scales that can be probed by the accelerator. In an accelerator, the beams might be made of electrons and positrons, protons and antiprotons, or ionized atoms. The faster they smash into each other, the finer the physics we probe with that experiment.
We typically smash electrically charged particle beams into each other,
for the simple reason that it is the easiest thing to do. Accelerating
charged particles can be done by electromagnetic fields (e.g. generated
by superconducting magnets), since they interact electromagnetically.
Neutral particles are more difficult to accelerate. (The reader should
compare this discussion with the discussion of how particles of the standard
model interact with each other, and as an exercise, can try to invent
accelerators based on the weak force, and find several reasons why they
would be problematic.)
Note also that from the above abstract description of experiments, we conclude that we should try to catch every bit of outgoing matter and radiation that is produced when we aim a beam at a target, or two beams at each other. When the outgoing matter is rapidly decaying, or very light and neutral, or extremely fast, that is a highly non-trivial task. If we catch none of the outgoing matter, it is rather evident that we will have gained no information from our contrived experiment.
Cern and Fermilab
We can be much more concrete about how these experiments are performed. There are in fact only a few places in the world with a microscope in the largest class, since they are extremely difficult to build, and cost a lot of money. There's the Tevatron in Fermilab (Chicago-Ilinois) and the LEP-LHC in Cern, Geneva, Switzerland. (There are many slightly smaller ones, which are admirable works of art too, of course.) I strongly urge the reader to check out the web sites of these huge experiments to uncover more of the detailed fascinating technique that goes into these machines. These accelerator usually have a very accessible web site, with lots of interesting information for the public and the press, including a gallery of impressive photographs of the accelerator. You'll see the tunnel, the way it is implanted in the local landscape, and usually you will find a map of the locations next to the tunnel where big labs are located. These are the places where particle bundles smash into each other and where the debris is gathered with large detectors. The large detectors and their associated labs usually have catchy names. The detectors are like onions, with different layers of the detector being suited for gathering different kinds of particles, or particular types of information on the particles that result from the collision (=scattering) of particle bundles, like their energy or charge. Usually you will find little information on the fascinating stories that tell how the impressive accuracy of the machine was technically achieved. (For example, the accelerator in Cern gave results with small deviations from expectations, and the deviations seemed to depend on the period of the month in which the results were obtained. After a long search, it turned out that the tidal forces of the moon had a tiny effect on the earth's crust that distorted the shape of the accelerator slightly, leading to the unexpected observations -- you see that once one is involved in extremely accurate measuring, one has to take into account all kinds of environmental effects. The more accurate the experiment, the more difficult it becomes to truly isolate it from outside circumstances.)